This invention relates to a light-sensitive silver halide photographic material. More particularly, it relates to a light-sensitive material used in photographing in the field of printing plate making, a scanner light-sensitive material, a contact light-sensitive material, and a facsimile light-sensitive material. It further relates to a light-sensitive silver halide photographic material that can be handled in a roomlight environment when used as a light-sensitive material particularly in the field of printing plate making or the like. From another aspect, this invention relates to a light-sensitive silver halide photographic material having a superior antistatic ability, that may cause less fog, has a high sensitivity, and yet can obtain a photographic image with a high contrast, and also can stably obtain a halftone with a high quality.
Light-sensitive silver halide photographic materials used in recent years in the field of printing plate making tend to be electrostatically charged in the course they are handled. In particular, in dry winter seasons, the charges caused by static electricity may reach as high as several kV, resulting in easy attraction of dust, and has caused generation of pin holes. It has had the problem of electrically shocking human bodies. To cope with these, countermeasures have been taken such that an earth is fitted, environmental humidity is increased, or light-sensitive silver halide photographic materials are made to contain various antistatic agents. These countermeasures, however, are not so satisfactory that, particularly in the case of conventional antistatic agents, their effect may turn almost lost after light-sensitive silver halide photographic materials have been processed through developing, fixing, washing and drying. Thus, it has been ernestly sought to provide a plate making light-sensitive material that can be kept antistatic even after the processing.
The light-sensitive silver halide photographic materials tend to be electrostatically charged particularly at low humidity as in the winter. It is particularly important to take the antistatic countermeasure when a high-sensitive photographic emulsion is coated at a high speed or a high-sensitive light-sensitive material is exposed to light through an automatic printer, as done in recent years.
As another problem in the conventional light-sensitive silver halide photographic materials, static marks may appear as a result of the discharge that occurs once the light-sensitive materials are electrostatically charged, or foreign matters such as dust may be attracted to cause generation of pinholes, resulting in an extreme deterioration of quality, and the repairment of which may bring about a serious lowering of operability. For this reason, commonly used in the light-sensitive silver halide photographic materials are antistatic agents. Recently used are fluorine-containing surface active agents, cationic surface active agents, amphoteric surface active agents, surface active agents or polymeric compounds containing a polyethylene oxide group, and polymers having in the molecule a sulfonic acid or phosphoric acid group.
In particular, frequently employed is charge arrangement adjustment using a fluorine-containing surface active agent, or conductivity improvement using a conductive polymer. For example, a technique in which an ionic polymer having a dissociation group in the polymer backbone chain is used is disclosed in Japanese Unexamined Patent Publications No. 91165/1974 and No. 121523/1974.
These conventional techniques, however, may bring about a great deterioration of antistatic abilities as a result of development processing. This is presumably because the antistatic abilities are lost after light-sensitive materials have gone through the developing step, acidic fixing step, and washing or the like step. Hence, the problem of the generation of pinholes due to attraction of dust may occur when a film having been processed is further used in printing as in printing light-sensitive materials.
Turning the viewpoint to the processing of light-sensitive silver halide photographic materials in a darkroom, in the field of printing plate making, a technique to make it possible to carry out under roomlight conditions the film making that has been hitherto carried out in a darkroom, i.e., the operation of the so-called contact step, has been sought in recent years for the purposes of labor-saving and improvement in a rationalized work environment, and thus improvements have been made in light-sensitive materials and in equipment such as printers.
The light-sensitive materials that can be handled under roomlight conditions include light-sensitive silver halide photographic materials having sensitivity to light of ultraviolet-rich light sources as exemplified by an ultrahigh-pressure mercury lamp, a metal halide light sources, a xenon lamp and a halogen lamp. These light-sensitive silver halide photographic materials can be handled under ordinary fluorescent lamps of as bright as 100 to 300 lux, or under fluorescent lamps for exclusive use, having a smaller amount of ultraviolet rays.
These light-sensitive materials have such an advantage, but, on the other hand have the disadvantage that the difficulties called pinholes tend to be generated in a black image obtained after the development processing.
The pinholes herein mentioned refer to the phenomenon that a blank area of not larger than about 30 .mu.m is made in a black image, and so named after its round or indefinite form which looks like a hole pierced with a pin.
As contact films used for duplicating an image from a fine-halftone image, no image reproduction with fidelity can be obtained if the film itself has an abnormal black area. To cope with this, the pinholes generated must be subjected to opaquing (i.e., an operation to stop up a hole to make image retouch), resulting in an extremely poor operating efficiency.
From such existing conditions, it has been strongly sought to provide a roomlight film that may cause the pinholes with difficulty.
Problems relating to special uses of light-sensitive silver halide photographic materials will be discussed below. In the field of the light-sensitive silver halide photographic material, a light-sensitive material feasible for obtaining a high-contrast image is often used depending on uses. For example, a photographic image with a high contrast is commonly used to form characters or halftone-dotted photographic images in the process of photographic plate making, or to form fine line images in the process of ultra-precision photographic plate making. A certain type of light-sensitive silver halide photographic materials used therefor are known to be capable of forming a photographic image with a very high contrast.
As having been conventionally done, a light-sensitive material comprising a silver chlorobromide emulsion having an average grain size of, for example, 0.2 .mu.m, having a narrow grains size distribution, with a uniform grain shape, and also having a high silver bromide content (at least 50 mol %) is processed using an alkaline hydroquinone developing solution having a low sulfite ion concentration. An image, e.g., a halftone image or fine line image, with a high contrast, high sharpness and high resolution can be thus obtained.
The light-sensitive silver halide photographic material of this type is known as a lith type light-sensitive material.
The process of photographic plate making comprises the step of converting an original with a continuous tone into a halftone image, in other words, the step of converting changes in density in the continuous tone of an original into aggregation of halftone dots having areas proportional to the density.
For this purpose, using the above lith type light-sensitive material, the original is photographed through a cross-line screen or a contact screen, followed by development processing to form a halftone image
Thus, the light-sensitive silver halide photographic material containing the silver halide emulsion comprising fine grains also having uniform grain size and grain form is used. Even when, however, the light-sensitive silver halide photographic material of this type is used, the dot quality and so forth are poorer when the processing is carried out using an ordinary black-and-white developing solution than when the developing was carried out using the lith type developing solution. For this reason, the processing is carried out using a developing solution called a lith developer which is low in sulfite ion concentration and uses hydroquinone single agent as a developing agent. Since, however, the lith developer, which is susceptible to automatic oxidation, has a very poor preservativity, it is sought to the utmost to provide a controlling method of constantly maintaining the quality of development even when the lith developer is continually used, and great efforts have been made so that the preservativity of this developing solution can be improved.
As a technique for such improvement, an automatic processor for photographic plate making commonly widely employs a system, so-called two-part separate replenishing system, in which separate replenishing solutions comprising a replenishing solution that compensates for what has deteriorated in the activity as a result of development processing (i.e., replenishment of processing fatigue) and a replenishing solution that compensates for what has undergone oxidation deterioration with time (i.e., replenishment of fatigue with time) are used to carry out replenishment. The above method, however, is required to control the balance of replenishment of the two solutions, and has the problem that the system must be made complicated in respect of apparatus and also in respect of operation.
On the other hand, a method is known in which processing is carried out using a developing solution having a high sulfite ion concentration to obtain a high-contrast image.
The above method employs a light-sensitive silver halide photographic material containing a hydrazine compound.
According to this method, sulfite ion concentration can be maintained at a high level in the developing solution, and processing can be carried out in the state that the preservativity has been enhanced.
However, the developing solution used for the light-sensitive silver halide photographic material containing a hydrazine compound requires to have a relatively high pH in order to obtain a high contrast, therefore tending to generate fog. In order to restrain this fog, various organic restrainers must be contained in a high concentration, so that there is the problem of sacrificing the sensitivity. For this reason, it is urgently sought to provide a light-sensitive silver halide photographic material that can obtain a high-contrast image, and also may generate less fog and has a high sensitivity.